Antistatic agent for plastics

ABSTRACT

(IN WHICH R4 is an alkyl group having 6 to 16 carbon atoms), R2 is a lower alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group of the same kind as R1, R3 is a lower alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4. WHEREIN R1 is a hydroxyalkyl group of the formula An antistatic agent for plastics comprising a compound of the formula;

United States Patent 119 Horikawa et a1.

1111 3,894,077 [4 1 July 8,1975

[ ANTISTATIC AGENT FOR PLASTICS [75] Inventors: Takeshi Horikawa; Hiroshi Yagihara; Masayoshi Kubo, all of Saitama, Japan [73] Assignee: Daicel Ltd., Osaka, Japan [22] Filed: Feb. 25, 1974 [21] Appl. No.: 445,587

[30] Foreign Application Priority Data Feb. 27, 1973 Japan 48-23518 [52] US. Cl 260/501.12; 260/563 R; 260/80.7;

260/85.5 R; 260/77.5 R; 260/78 R; 260/92.8 R; 260/93.5 C; 260/D1G. 20

FOREIGN PATENTS OR APPLICATIONS 4,226,523 12/1967 Japan 260/501.12

1,077,772 8/1967 United Kingdom 260/50I.12

Primary Examiner-Howard T. Mars Assistant ExaminerNicky Chan Attorney, Agent, or Firm-Woodhams, Blanchard and Flynn [57] ABSTRACT An antistatic agent for plastics comprising a compound of the formula;

wherein R is a hydroxyalkyl group of the formula (in which R, is an alkyl group having 6 to 16 carbon atoms), R is a lower alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group of the same kind as R,, R is a lower alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 4.

3 Claims, No Drawings ANTISTATIC AGENT FOR PLASTICS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a novel antistatic agent for plastics,

2. Description of the Prior Art In general, plastics have a higher electric insulation resistance than other materials. Accordingly, plastics are readily statically charged by friction and many troubles are caused by static charges. As a familiar exam ple, an unpleasant pricking irritation is given to human bodies when garments of synthetic fibers are worn, or dust is adsorbed on a plastic molded article to injure the appearance thereof. Further, at the step of processing plastics or on handling thereof, static charges bring about various troubles such as accumulation of dust at the compounding step or an electric shock given to human bodies at the processing step.

Accordingly, it is important to prevent generation and/or accumulation of static electricity during the step of molding plastics and in the molded plastic articles. As means for preventing such generation or accumulation of static charges, there have heretofore been proposed and studied various methods, including a method comprising coating the surface of a plastic molded article with a surface active agent having an antistatic property, a method comprising mechanically kneading the antistatic agent into the plastic material prior to the molding step, and other similar methods.

However, when an antistatic agent for plastics is ac tually employed, not only the antistatic property but also various practical conditions such as influences on inherent properties of plastics, the safety to human bodies, troubles at the molding and processing steps and the change of quality with the lapse of time should be taken into consideration. Moreover, it is desired that the antistatic agent has a suitable compatibility with plastics and it causes neither blooming nor discoloration. A method comprising kneading an antistatic agent into a plastic material is especially adopted for attaining a durable antistatic effect, but most antistatic agents used in this method are unstable at high temperatures adopted at the processing step and tend to cause such undesired phenomena as decomposition and discoloration.

SUMMARY OF THE INVENTION The purpose of the present invention is to provide an antistatic agent for plastics which is stable at high temperatures at the processing step and causes neither decomposition nor discoloration when kneaded into a plastic material, which improves the lubricating property and processability of a plastic material, and which has a suitable compatibility with a plastic material and causes '10 inter-action with other additives such as a plasticizer, a stabilizer and the like. We have discovered that a compound represented by the following general formula;

wherein R is a hydroxyalkyl group represented by the general formula (in which R, stands for an alkyl group having 6 to l6 carbon atoms), R stands for a lower alkyl group having 1 to 4 carbon atoms or a hydroxyalkyl group of the same kind as R,, R is a lower alkyl group having I to 4 carbon atoms, and n is an integer of l to 4, has excellent effects as an antistatic agent for plastics. Japanese Pat. Publication No. 26523/67 discloses an antistatic agent composed ofa compound of a structure similar to that of the above compound of this invention, namely a compound represented by the following formula;

ll 55 H l 'l (CH2) 3SO3 CIl wherein n is an integer of l2 to [6. However, as is illustrated in Examples given hereinafter, the antistatic agent of this invention has a much higher antistatic effect than the above known analogous compound. and when the antistatic agent of this invention is kneaded into a plastic material, it is stable at high temperatures and causes neither decomposition nor discoloration. Thus, in the compound of this invention, the presence of the hydroxyl group results in a prominent antistatic effect and a good stability at high temperatures.

The compound represented by the above general formula (l) is a novel compound which can be prepared by a combination of several known methods in the following manner.

An a-olefin obtained by, for example, oligomerization of ethylene or thermal decomposition of paraffin is reacted with a peracid such as peracetic acid or an epoxidation agent such as hydroperoxide to form an a-olefin oxide, and then it is reacted with a primary amine or a secondary amine to form a tertiary amine. The aimed compound represented by the above formula (l) is formed by reacting the thus obtained tertiary amine with a sultone. This reaction between the tertiary amine and the sultone is generally carried out in the presence of an alcohol as a solvent.

In case the obtained reaction product is used as an antistatic agent in this invention, it is necessary to remove the solvent therefrom, and, for this purpose, a conventional desolvation process can be adopted.

Further, we have studied and developed a method for preparing the compound of this invention more effectively, in which the above tertiary amine is reacted directly with a sultone in the absence ofa solvent by employing a reaction vessel having a function of kneading and mixing highly viscous materials efficiently, such as a kneader, to obtain the antistatic agent of this invention easily without the necessity of such processes as separation or purification. In this method, the mole ratio of the fed tertiary amine to the sultone is maintained at l, and the reaction is carried out at 50 to 140C, preferably 70 to C, for l to l0 hours, preferably 3 to 5 hours. It has been found that according to this method the aimed compound can be obtained in such a high yield as 98% or higher and the quality of the product is better than that of the product obtained ac cording to the method using a solvent.

The amount of the antistatic agent to be kneaded into a plastic molding composition varies depending on the particular kind of the plastic material employed, but it is generally preferred that the antistatic agent is used in an amount of 0.l to 5.0 percent by weight, especially 0.3 to 3 percent by weight based on the weight of the plastic material.

The antistatic agent of this invention has a suitable compatibility with various thermoplastic resins such as homopolymers and copolymers, such as vinyl chloride vinyl acetate copolymers, of vinyl chloride, polystyrene resins including acrylonitrile-styrene (AS) or acryloni' trilebutadiene-styrene (ABS) copolymer resins, polethylene, polypropylene and other poly(a-olefins), polyamide resins, polycarbonate resins, etc., and it is very stable at high temperatures Therefore, when the antistatic agent of this invention is kneaded into these thermoplastic resins, they can be processed and molded with ease. It has been found that the antistatic agent of this invention exhibits a good lubricating property at the molding step and improves the moldability of the resin compound. Further, because of the presence of a long-chain, saturated alkyl group, the antistatic agent of this invention is slightly soluble in water and, hence, it has a good water resistance. The com pound of this invention is not only very excellent in the original antistatic effect but also shows little change in this high effect with the lapse of time. Moreover, the antistatic agent of this invention is not poisonous and gives no irritation to the skin, and, therefore, it can be added at the processing step. These are advantages of the antistatic agent of this invention.

The excellent effects attained by the antistatic agent of this invention will now be illustrated more in detail by reference to the following examples, but the scope of the invention is not limited by these examples which are given for purposes of illustration only,

PREPARATION EXAMPLE I 104 Parts of an alkylene oxide mixture obtained by under agitation at 80C for 4 hours in a sealed reaction vessel. After completion of the reaction, the solvent and unreacted dimethylamine were removed by distillation under reduced pressure to obtain l25.3 parts of 5 the corresponding tertiary amine. Then, 130 parts of the thus obtained tertiary amine was admixed with 62 parts of propane sultone and 300 parts of isopropyl alcohol as a solvent, and the reaction was carried out for 3 hours by heating the mixture at 50C. Then, the reaction mixture was cooled to room temperature, and precipitates were recovered by filtration under reduced pressure to obtain 200 parts of a white waxy solid having a melting point of l40 C, in which the amine content was 0.8 percent by weight. The compound obtained in this Preparation Example I is designated as "antistatic agent A."

PREPARATION EXAMPLE 2 An autoclave was charged with 400 parts of a mixture of alkylene oxides having 16 and I8 carbon atoms, respectively, 213 parts of an aqueous solution containing 40 percent by weight of dimethylamine and 200 parts of methyl alcohol, and the mixture was reacted at 100C for 6 hours. In the same manner as described in Preparation Example I, 465 parts of the corresponding tertiary amine was recovered from the reaction mixture. Then, I37 parts of the thus obtained tertiary amine was admixed with 49 parts of propane sultone and 240 parts of isopropyl alcohol, and the reaction was carried out at 60 to 70C for 4 hours. In the same manner as described in Preparation Example l, 180 parts of a white waxy solid having a melting point of l60C was recovered from the reaction mixture. The compound obtained in this Preparation Example 2 is designated as antistatic agent B.

PREPARATION EXAMPLES 3 AND 4 Antistatic agents C and D were prepared from alkylene oxides having 8 and I0 carbon atoms, respectively, according to the method described in Preparation Example l. Reaction conditions and results are summarized in Table I.

treating a mixture of a-olefins having l2 and 14 carbon atoms, respectively, with peracetic acid was incorporated with 67.7 parts of an aqueous solution containing 40% by weight of dimethylamine and I23 parts of iso propyl alcohol as a solvent, and the mixture was heated The antistatic agent D was recrystallized from etha' nol and sufficiently dried to obtain needle crystals having a melting point of l7l 172C. Then, the antistatic agent D was subjected to identification by IR, NMR and elementary analysis. Results are as follows:

l Infrared Absorption Spectrum Analysis:

lllStl cm 120" cm "1 characteristic absorption bands owing to $0 3451) cm"; characteristic absorption band owing to OH 2. Nuclear Magnetic Resonance Spectrum Analysis:

EXAMPLE I lOO Parts of a vinyl chloride resin (polymerization degree of 800), 2.5 parts ofa stabilizer (dibutyl tin maleate), parts of a plasticizer (dioctyl phthalate) and 0.5 part of the antistatic agents A, B of this invention were sufficiently mixed and kneaded at [C for 5 hydrogen number ratio* the hydrogen number ratio was determined from the integration curve 3 Elementary Analysis:

Theoretical Value Found Value t.') :t1t i carbon 55.73% 55.6954 marti n 10.42% 10.28?! nitrogen 424? 43334 iron] the foregoing results the antistatic agent D was identified as a compound having the following struc- 45 OH CH Antistatic agents A to D prepared in Preparation Examples l to 4 were tested as samples in the following Examples.

minutes by means of a hot roll. Then, the kneaded resin compound was molded into sheets of 0.6 to 1.0 mm in thickness, and several sheets were piled and pressed at C to obtain a sheet of 1.5 mm in thickness.

The antistatic effect in the resulting sheet was determined by employing a static honest meter (trade name, manufactured by Shishido Shokai) and Ultra Megohmmeter Model SM-lO (Toa Electronics LTD). As a comparative sample, an antistatic agent having a structure similar to that of the antistatic agent of this invention and represented by the following formula;

was tested under the same conditions. Results are shown in Table 2.

In the tables, the term means that no reduction of the initial electric charge was observed.

. H Surface Resistivity Heat Resistance Proces- AntlstatiC Agent Half Life (C)! 30 min) sability Remarks 1) antistatic agent A 4 seconds 3.2 x 10 slightly good product of colored this invention 2) antistatic agent B 22 seconds 9.0 x 10 slightly good product of colored this invention Table 2 -Cuntinued Antistatic Agent Half Life surfacefiieslstlvlty g 'ga g gg? :Zgiiig Remarks blank w 8.0 x 10 slightly somewhat control colored bad l2 C l| -N (Cl l -S w 8.5 x yellowish good comparative l brown sample CH (n=l2,14)

1.0 Part of the antistatic agent of this invention was uniformly blended into a so-called record compound comprising I00 parts of a vinyl chloride-vinyl acetate copolymer resin (polymerization degree of 450), L5 parts of an epoxidized soybean oil (oxirane content=7.0 percent), 1.0 part of a stabilizer (di-n-octyltin-5,5'-bis(iso-octylmercaptoacetate) and 0.3 part of a lubricant (calcium stearate), and the blend was kneaded at I50C for 5 minutes by means of a hot roll. The kneaded compound was formed into sheets of 0.6 to 1.0 mm in thickness and several sheets were piled and pressed at 170C to obtain a sheet of L5 mm in thickness. The properties of the resulting sheet were determined and compared in the same manner as in Example to obtain results shown in Table 3.

100 Parts of a commercially available ABS resin (a and the blend was mixed and kneaded at l85C for 5 minutes to obtain a sheet of 0.6 to 1.0 mm in thickness. The resulting sheet was cut into pellets ofS mm X 5 mm in size. The pellets were molded into an article mm X 50 mm X 2 mm in size by employing an Arburg universal injection molding machine (Model C4/D manufactured by Western Trading Co). The antistatic characteristics of the resulting molded articles were determined in the same manner as in Example I to obtain results shown in Table 4.

tie agent A, B, C or D of this invention or a comparative antistatic agent having a structure similar to that of the antistatic agent of this invention and represented by the formula raft co ol mer obtained from 6 parts of styrene- C H so (11:14, 16 g P Y n 2n+l 2 3 3 butadiene rubber, 72 parts of styrene and 28 parts of (I: acrylonitrile) was blended with 1.5 parts of the antista- 35 Table 3 Antistatic Half Life Surface Heat Resistance Proces- Agent (seconds) resisgvity (180C X 10 min) sability antistatic 18 3.2 X [0" slightly good agent A colored blank 1; 21 X l0 slightly slightly colored bad commercially 48 8.5 X It) yellowed slightly available bad product One Day One Week Antistatic chlgitgg Molding chili-12:; Molding Agent voltage half life 8 half life (mv) (seconds) (seconds) antistatic agent A 95 2 l antistatic agent B antistatic agent C 3 2 antistatic agent D a n n C ll I}! (CH S0 24 23 CH ,(n=l4 16) blank From the results shown above, it is seen that each of the antistatic agents of this invention is superior to the comparative antistatic agent having a similar structure and represented by the formula;

wherein R is hydroxyalkyl having the formula in which R, is alkyl having 6 to 16 carbon atoms, R, is the same as R or alkyl having I to 4 carbon atoms. and R is alkyl having I to 4 carbon atoms.

2. An antistatic agent according to claim 1, in which R and R are methyl.

3. An antistatic agent of the formula;

wherein R, is hydroxyalkyl having the formula in which R is alkyl having 6 to l6 carbon atoms, R, is the same as R, or alkyl having I to 4 carbon atoms, and R is alkyl having I to 4 carbon atoms.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 894 077 D d July 8, 1975 Takeshi Horikawa, Hiroshi Yagihara Inventor(s) and Masayoshi Kubo It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 9, line 20; correct the formula to read as follows:

2 I R (cH s0 Signed and Scaled this Arrest:

RUTH C. MASON C. MARSHALL DANN :lltmting Officer RM O- 1 USCOMM-DC B0376-P69 U5 GOVERNIIENY PRINYINQ DFVILE 

1. AN ANTISTATIC AGENT OF THE FORMULA
 2. An antistatic agent according to claim 1, in which R2 and R3 are methyl.
 3. An antistatic agent of the formula; 